I've found that a ZFS cluster is the best solution for your kind of problem. ZFS has its own awesome software RAID system. You could get six 3TB drives, use two

I've found that a ZFS cluster is the best solution for your kind of problem. ZFS has its own awesome software RAID system. You could get six 3TB drives, use two of those drives for redundancy with RAID-Z2, and then get 12TB of ultra-reliable private storage.